Use Z-offset to detect the end of heat soak

heat_soak.cfg

# Macros for automating heat soak.
# Will measure the Z-offset using the Auto-Z-Calibration plugin every few minutes.
# Keeps track of how much the offset is changing between measurements.
# When the delta falls below a threshold, stops measuring and starts the print queue.
#
# ASSUMPTIONS
# 1. You are using Klicky Probe (this is a prerequisite for the Auto-Z-Calibration plugin)
# 2. Auto-Z-Calibration plugin is installed and configured
#
# DEFAULTS
# By experimentation, we have found that a measurement interval of 6 minutes (360 seconds)
# and a delta-tolerance of 0.025mm brings the printer to thermal equilibrium in about 45 minutes.
# This is for a Voron V2r1 350x350 and may be significantly different for other printers.
#
# Determining your own parameters
# TOLERANCE
# To determine the tolerance value, we heat-soaked our printer for more than an hour starting from cold, performing
# A z-offset measurement and 10x10 bed mesh every few minutes. We plotted the change in Z offset (delta-Z)
# along with cumulative Z offset against time on a graph in Excel.
# You can then pick the maximum amount of Z-offset error you are prepared to tolerate on your first layer,
# and look up the corresponding delta-Z value, which you can use as your Tolerance parameter in this GCode macro.
#
# The measurement interval is a bit more subjective. It needs to be long enough to allow a detectable change in delta-Z,
# But short enough that thermal equilibrium is detected without wasting too much time.
# We found that "about 6 minutes" was a good starting point and you may adjust this up or down depending on
# how accurate you want to be (longer) vs. how impatient you are (shorter).
# Whatever value you decide on, we recommend plotting your delte-Z graph using that time interval.

[gcode_macro HEATSOAK]
variable_tolerance: 0.0175
variable_previous_offset: 0
variable_delta: 0
variable_repeat_seconds: 180
gcode:
  {% set Threshold = params.TOLERANCE | default(0.025) | float %}  
  {% set Repeat = params.INTERVAL | default(360) | int %}
  SET_GCODE_VARIABLE MACRO=HEATSOAK VARIABLE=tolerance VALUE={Threshold}
  SET_GCODE_VARIABLE MACRO=HEATSOAK VARIABLE=repeat_seconds VALUE={Repeat}
  M117 Heatsoak starting
  # PRINTER_STATE_PREHEAT - sets LED state
  UPDATE_DELAYED_GCODE ID=_HEATSOAK_CHECK_Z_OFFSET DURATION=5

[gcode_macro HEATSOAK_STOP]
gcode:
  UPDATE_DELAYED_GCODE ID=_HEATSOAK_CHECK_Z_OFFSET DURATION=0

[delayed_gcode _HEATSOAK_CHECK_Z_OFFSET]
initial_duration: 0
gcode:
  {action_respond_info("Measuring Z offset")}
  CALIBRATE_Z FORCE=1
  _HEATSOAK_COMPUTE_DELTA
  _HEATSOAK_RESCHEDULE

[gcode_macro _HEATSOAK_COMPUTE_DELTA]
gcode:
  {% set previous = printer["gcode_macro HEATSOAK"].previous_offset %}
  {% set current = printer.gcode_move.homing_origin.z %}
  {% set delta = current - previous %}
  {% set tolerance = printer["gcode_macro HEATSOAK"].tolerance %}
  SET_GCODE_VARIABLE MACRO=HEATSOAK VARIABLE=previous_offset VALUE={current}
  SET_GCODE_VARIABLE MACRO=HEATSOAK VARIABLE=delta VALUE={delta}
  {action_respond_info("Previous:  %.3f" % (previous))}
  {action_respond_info("Current:   %.3f" % (current))}
  {action_respond_info("Delta:     %.3f" % (delta))}
  {action_respond_info("Tolerance: %.3f" % (tolerance))}

[gcode_macro _HEATSOAK_RESCHEDULE]
gcode:
  {% set previous = printer["gcode_macro HEATSOAK"].previous_offset %}
  {% set current = printer.gcode_move.homing_origin.z %}
  {% set delta = printer["gcode_macro HEATSOAK"].delta %}
  {% set tolerance = printer["gcode_macro HEATSOAK"].tolerance %}
  {% set repeat = printer["gcode_macro HEATSOAK"].repeat_seconds %}
  {% if delta|abs <= tolerance %}
    # PRINTER_STATE_SUCCESS sets LED state
    M117 Heatsoak Complete
    BEEP DURATION=2000
    HEATSOAK_STOP
    { action_call_remote_method("start_job_queue") }
  {% else %}
    M117 D{delta} T{tolerance}
    UPDATE_DELAYED_GCODE ID=_HEATSOAK_CHECK_Z_OFFSET DURATION={repeat}
  {% endif %}